题解 | 对商品的销售情况进行深度分析

关键：表合并；比例的计算：无需CTE子查询，用窗口函数解决分组计算

select category product_category
,age_group
,sum(quantity*price) total_sales_amount
,round(sum(quantity*price)/sum(sum(quantity*price))over(partition by category),2) purchase_percentage
from sales s left join customer_info c on s.sale_id=c.sale_id
left join products p on s.product_id=p.product_id
group by category,age_group
order by category,age_group